title: Effectiveness of bisphosphonate therapy in a community setting.
abstract: BACKGROUND
  Osteoporosis is a major cause of morbidity and mortality. Clinical trials have shown the effectiveness of bisphosphonates, the most commonly prescribed treatments, in reducing fracture risk. The population-based effectiveness of bisphosphonates in clinical practice is uncertain.
  
  
  METHODS
  This retrospective cohort study used a matched design that compared time to clinical fracture in at-risk community women who initiated a bisphosphonate medication between 7/1/1996 and 6/30/2006 to those who did not. The study was conducted in an HMO in Oregon and Washington. Clinical electronic databases provided data. Eligible members were newly treated women aged > or = 55 years with either a BMD T-score of < or = -2.0 or a prior qualifying clinical fracture. They did not have contraindications for bisphosphonate therapy or a diagnosis associated with secondary osteoporosis (n=1829). They were matched to a similar comparison group (n=1829; total N=3658). The primary outcome was the first new incident fracture validated through chart review (closed clinical fracture of any bone except face, skull, finger, or toe or pathological fracture secondary to malignancy) during follow-up. An intention-to-treat analysis used Cox proportional hazards models to estimate the hazard ratio of fracture for treated relative to comparison patients, adjusting for differences in potential confounders.
  
  
  RESULTS
  Treated and comparison patients were similar in mean age (72.0 years) and history of fracture (about 45%). The treated group had more women with T-scores of < or = -2.5 (67.3% vs. 54.7%) and a lower mean weight (146.6 lb vs. 151.8 lb). Only about 45% of treated patients had a bisphosphonate medication possession ratio (MPR) of > or = 0.80. During follow-up, 198 (10.8%) of patients in the treated group had incident fractures, vs. 179 (9.8%) of patients in the comparison group. After adjustments, patients in the treated group were 0.91 (95% CI 0.74-1.13) as likely to have an incident fracture as the comparison patients (p=0.388). The treatment effect remained non-significant after accounting for MPR.
  
  
  CONCLUSIONS
  In this analysis of a community cohort of post-menopausal women at risk, the fracture risk of patients who received bisphosphonates did not differ significantly from those who did not. An enhanced understanding of this lack of treatment effect is urgently needed.
authors.affiliation: Center for Health Research, Kaiser Permanente Northwest, Portland, OR 97227, USA. Adrianne.C.Feldstein@kpchr.org
authors.forename: Adrianne C
authors.initials: AC
authors.lastname: Feldstein
authors.forename: Derek
authors.initials: D
authors.lastname: Weycker
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Nichols
authors.forename: Gerry
authors.initials: G
authors.lastname: Oster
authors.forename: Gabriela
authors.initials: G
authors.lastname: Rosales
authors.forename: David L
authors.initials: DL
authors.lastname: Boardman
authors.forename: Nancy
authors.initials: N
authors.lastname: Perrin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004164:Diphosphonates / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D050723:Fractures, Bone / Q000150:complications; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications / Q000188:drug therapy; D016016:Proportional Hazards Models; D012111:Residence Characteristics; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D004164:Diphosphonates